I/O Addresses
PCI-8255 + DOS
The PCI 8255 is compatible with the ISA version 8255-N. DOS software can continue to be used
without modification. Since no fixed address can be set on the PCI card by PnP, the setting must
be made in the AUTOEXEC with the 8255SET software. Program and instructions can be found
on the CD.
If the DOS software can still be modified, it is also possible to query the PnP. Instructions can be
found on the next page.
Due to the PCI bus, no more BUS clock can be used for the timer. The clock must be supplied
externally!
PCI- DOS
To use the PCI cards under DOS, the base address in the port I/O area of the computer must first be determined
will be. As soon as the base address is known, simple port I/O commands can be written to the board with simple port I/O com-
mands, e.g. in assembler
mov dx,BasisAddresse
mov al,ZuSchreibenderWert
out dx,al
or:
mov dx,BasisAddresse
i
n al,dx
can be accessed.
The base address of a PCI card is initially assigned by the BIOS, and may change at each startup of the computer.
The BIOS provides some additional functions for PCI cards via the special interrupt 15h.
is being resorted to.
Since each PCI card is identified by a unique manufacturer number (VendorID) and a card number (DeviceID)
you must adjust the corresponding values for the inserted card. Below is also a list
of the current cards, and the corresponding DeviceID‘s.
Base +
0
Port 1A input/output buffer
1
Port 1B input/output buffer
2
Port 1C input/output buffer
3
Port 1 control register
4
Port 2A input/output buffer
5
Port 2B input/output buffer
6
Port 2C input/output buffer
7
Port 2 control register
8
Counter 0 input/output buffer
9
Counter 1 input/output buffer
A
Counter 2 input/output buffer
B
Counter control register
